package DynamicProgramming;

/**
 * @author Kshitij VERMA (github.com/kv19971) LEVENSHTEIN DISTANCE dyamic programming implementation
 *     to show the difference between two strings
 *     (https://en.wikipedia.org/wiki/Levenshtein_distance)
 */
public class LevenshteinDistance {
  private static int minimum(int a, int b, int c) {
    if (a < b && a < c) {
      return a;
    } else if (b < a && b < c) {
      return b;
    } else {
      return c;
    }
  }

  private static int calculate_distance(String a, String b) {
    int len_a = a.length() + 1;
    int len_b = b.length() + 1;
    int[][] distance_mat = new int[len_a][len_b];
    for (int i = 0; i < len_a; i++) {
      distance_mat[i][0] = i;
    }
    for (int j = 0; j < len_b; j++) {
      distance_mat[0][j] = j;
    }
    for (int i = 0; i < len_a; i++) {
      for (int j = 0; j < len_b; j++) {
        int cost;
        if (a.charAt(i) == b.charAt(j)) {
          cost = 0;
        } else {
          cost = 1;
        }
        distance_mat[i][j] =
            minimum(distance_mat[i - 1][j], distance_mat[i - 1][j - 1], distance_mat[i][j - 1])
                + cost;
      }
    }
    return distance_mat[len_a - 1][len_b - 1];
  }

  public static void main(String[] args) {
    String a = ""; // enter your string here
    String b = ""; // enter your string here

    System.out.print("Levenshtein distance between " + a + " and " + b + " is: ");
    System.out.println(calculate_distance(a, b));
  }
}
